Stress diffuser

ABSTRACT

means are provided for diffusing stresses, particularly in couplings between vertical heater tubes 2 and the connection to a tube (pigtail) 3 leading to a manifold, arising from temperature changes during start-up or shut-down, bending moments and vibration during operation. The stress diffuser may be installed at the connection of the manifold connection such as a &#34;pigtail&#34;, to a heater tube and is constituted by a short tube 1 machined to varying inside diameter (preferably constant OD) by tapered wall thickness from a mid-section of maximum wall thickness to lesser wall thickness toward the ends of the stress diffuser. For ease of repair and replacement, the stress diffuser is fitted in a collar 4 on the heater tube.



